The present invention relates in general to magnetic apparatus, and pertains, more particularly, to a new construction of magnetic amplifier. Even more particularly, the invention pertains to a magnetic amplifier with a single multi-legged ferrite core operating on the principle of a saturable mutual inductance bridge. The principles of the present invention may also be employed in the construction of magnetometers and of magnetostrictive strain meters, or, in general, to the construction of devices to be used for the detection and measurement of any physical phenomenon, producing small magnetic signals in the core of the magnetic amplifier itself.
With regard to prior art patents relating to the field of magnetic amplifiers in general, the following are typical: U.S. Pat. Nos. 2,164,383; 3,015,073; 3,271,690; 4,286,211; 3,801,907; and 4,339,792. Of the foregoing patents, the latter U.S. Pat. No. 4,339,792 is typical and illustrates a multi-leg ferrite core construction. However, it is noted that this device is not used for signal amplification. It appears to be used as a regulator in connection with a power supply. Also, in most of these prior patents, it is noted that they make use of rectifiers in the excitation circuit which is not necessary in accordance with the principles of the present invention. In accordance with the present invention, the legs of the core are operating on both halves of the cycle. Another magnetic amplifier related to the background of the present invention is described in: IEEE Transactions on Magnetics, vol 1, June 1965, pp 87-90.
The above referred to prior art patents and publication operate on the principle of saturable reactors or inductors in which the effect of the non-linear magnetic material reflects on the same coil on which the excitation current is sent, or in another coil that is strongly coupled to it. On the other hand, in accordance with the present invention, the principle of operation is one of unbalancing a bridge of four saturable mutual inductances, and in which the effect of the non-linear material takes place in an output coil that becomes coupled to the excitation coil only when the input current is different from zero.
Accordingly, it is an object of the present invention to provide an improved magnetic amplifier characterized by improved amplifier gain.
Another object of the present invention is to provide a magnetic amplifier with a single multi-legged ferrite core and that one embodiment has a magnetic amplification with a power gain of 100 for a predetermined frequency range. The power gain is here defined, for small input signals, as the ratio between the power obtainable from the output coil (at the expense of the excitation power) and the power dissipated into the input coil.
Still another object of the present invention is to provide an improved magnetic amplifier that is relatively simple in construction, that can be constructed and operated with ease, and that operates on the principle of saturable mutual inductance bridge.